1. 根目录:
2. include
3. net
4. route.h

/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET  is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Definitions for the IP router.
 *
 * Version:	@(#)route.h	1.0.4	05/27/93
 *
 * Authors:	Ross Biro
 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 * Fixes:
 *		Alan Cox	:	Reformatted. Added ip_rt_local()
 *		Alan Cox	:	Support for TCP parameters.
 *		Alexey Kuznetsov:	Major changes for new routing code.
 *		Mike McLagan    :	Routing by source
 *		Robert Olsson   :	Added rt_cache statistics
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 */
#ifndef _ROUTE_H
#define _ROUTE_H

#include <net/dst.h>
#include <net/inetpeer.h>
#include <net/flow.h>
#include <net/inet_sock.h>
#include <linux/in_route.h>
#include <linux/rtnetlink.h>
#include <linux/rcupdate.h>
#include <linux/route.h>
#include <linux/ip.h>
#include <linux/cache.h>
#include <linux/security.h>

/* IPv4 datagram length is stored into 16bit field (tot_len) */
#define IP_MAX_MTU	0xFFFFU

#define RTO_ONLINK	0x01

#define RT_CONN_FLAGS(sk)   (RT_TOS(inet_sk(sk)->tos) | sock_flag(sk, SOCK_LOCALROUTE))
#define RT_CONN_FLAGS_TOS(sk,tos)   (RT_TOS(tos) | sock_flag(sk, SOCK_LOCALROUTE))

struct fib_nh;
struct fib_info;
struct rtable {
	struct dst_entry	dst;

	int			rt_genid;
	unsigned int		rt_flags;
	__u16			rt_type;
	__u8			rt_is_input;
	__u8			rt_uses_gateway;

	int			rt_iif;

	/* Info on neighbour */
	__be32			rt_gateway;

	/* Miscellaneous cached information */
	u32			rt_pmtu;

	struct list_head	rt_uncached;
};

static inline bool rt_is_input_route(const struct rtable *rt)
{
	return rt->rt_is_input != 0;
}

static inline bool rt_is_output_route(const struct rtable *rt)
{
	return rt->rt_is_input == 0;
}

static inline __be32 rt_nexthop(const struct rtable *rt, __be32 daddr)
{
	if (rt->rt_gateway)
		return rt->rt_gateway;
	return daddr;
}

struct ip_rt_acct {
	__u32 	o_bytes;
	__u32 	o_packets;
	__u32 	i_bytes;
	__u32 	i_packets;
};

struct rt_cache_stat {
        unsigned int in_slow_tot;
        unsigned int in_slow_mc;
        unsigned int in_no_route;
        unsigned int in_brd;
        unsigned int in_martian_dst;
        unsigned int in_martian_src;
        unsigned int out_slow_tot;
        unsigned int out_slow_mc;
};

extern struct ip_rt_acct __percpu *ip_rt_acct;

struct in_device;

int ip_rt_init(void);
void rt_cache_flush(struct net *net);
void rt_flush_dev(struct net_device *dev);
struct rtable *__ip_route_output_key(struct net *, struct flowi4 *flp);
struct rtable *ip_route_output_flow(struct net *, struct flowi4 *flp,
				    struct sock *sk);
struct dst_entry *ipv4_blackhole_route(struct net *net,
				       struct dst_entry *dst_orig);

static inline struct rtable *ip_route_output_key(struct net *net, struct flowi4 *flp)
{
	return ip_route_output_flow(net, flp, NULL);
}

static inline struct rtable *ip_route_output(struct net *net, __be32 daddr,
					     __be32 saddr, u8 tos, int oif)
{
	struct flowi4 fl4 = {
		.flowi4_oif = oif,
		.flowi4_tos = tos,
		.daddr = daddr,
		.saddr = saddr,
	};
	return ip_route_output_key(net, &fl4);
}

static inline struct rtable *ip_route_output_ports(struct net *net, struct flowi4 *fl4,
						   struct sock *sk,
						   __be32 daddr, __be32 saddr,
						   __be16 dport, __be16 sport,
						   __u8 proto, __u8 tos, int oif)
{
	flowi4_init_output(fl4, oif, sk ? sk->sk_mark : 0, tos,
			   RT_SCOPE_UNIVERSE, proto,
			   sk ? inet_sk_flowi_flags(sk) : 0,
			   daddr, saddr, dport, sport,
			   sk ? sock_i_uid(sk) : GLOBAL_ROOT_UID);
	if (sk)
		security_sk_classify_flow(sk, flowi4_to_flowi(fl4));
	return ip_route_output_flow(net, fl4, sk);
}

static inline struct rtable *ip_route_output_gre(struct net *net, struct flowi4 *fl4,
						 __be32 daddr, __be32 saddr,
						 __be32 gre_key, __u8 tos, int oif)
{
	memset(fl4, 0, sizeof(*fl4));
	fl4->flowi4_oif = oif;
	fl4->daddr = daddr;
	fl4->saddr = saddr;
	fl4->flowi4_tos = tos;
	fl4->flowi4_proto = IPPROTO_GRE;
	fl4->fl4_gre_key = gre_key;
	return ip_route_output_key(net, fl4);
}

int ip_route_input_noref(struct sk_buff *skb, __be32 dst, __be32 src,
			 u8 tos, struct net_device *devin);

static inline int ip_route_input(struct sk_buff *skb, __be32 dst, __be32 src,
				 u8 tos, struct net_device *devin)
{
	int err;

	rcu_read_lock();
	err = ip_route_input_noref(skb, dst, src, tos, devin);
	if (!err)
		skb_dst_force(skb);
	rcu_read_unlock();

	return err;
}

void ipv4_update_pmtu(struct sk_buff *skb, struct net *net, u32 mtu, int oif,
		      u32 mark, u8 protocol, int flow_flags);
void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu);
void ipv4_redirect(struct sk_buff *skb, struct net *net, int oif, u32 mark,
		   u8 protocol, int flow_flags);
void ipv4_sk_redirect(struct sk_buff *skb, struct sock *sk);
void ip_rt_send_redirect(struct sk_buff *skb);

unsigned int inet_addr_type(struct net *net, __be32 addr);
unsigned int inet_dev_addr_type(struct net *net, const struct net_device *dev,
				__be32 addr);
void ip_rt_multicast_event(struct in_device *);
int ip_rt_ioctl(struct net *, unsigned int cmd, void __user *arg);
void ip_rt_get_source(u8 *src, struct sk_buff *skb, struct rtable *rt);

struct in_ifaddr;
void fib_add_ifaddr(struct in_ifaddr *);
void fib_del_ifaddr(struct in_ifaddr *, struct in_ifaddr *);

static inline void ip_rt_put(struct rtable *rt)
{
	/* dst_release() accepts a NULL parameter.
	 * We rely on dst being first structure in struct rtable
	 */
	BUILD_BUG_ON(offsetof(struct rtable, dst) != 0);
	dst_release(&rt->dst);
}

#define IPTOS_RT_MASK	(IPTOS_TOS_MASK & ~3)

extern const __u8 ip_tos2prio[16];

static inline char rt_tos2priority(u8 tos)
{
	return ip_tos2prio[IPTOS_TOS(tos)>>1];
}

/* ip_route_connect() and ip_route_newports() work in tandem whilst
 * binding a socket for a new outgoing connection.
 *
 * In order to use IPSEC properly, we must, in the end, have a
 * route that was looked up using all available keys including source
 * and destination ports.
 *
 * However, if a source port needs to be allocated (the user specified
 * a wildcard source port) we need to obtain addressing information
 * in order to perform that allocation.
 *
 * So ip_route_connect() looks up a route using wildcarded source and
 * destination ports in the key, simply so that we can get a pair of
 * addresses to use for port allocation.
 *
 * Later, once the ports are allocated, ip_route_newports() will make
 * another route lookup if needed to make sure we catch any IPSEC
 * rules keyed on the port information.
 *
 * The callers allocate the flow key on their stack, and must pass in
 * the same flowi4 object to both the ip_route_connect() and the
 * ip_route_newports() calls.
 */

static inline void ip_route_connect_init(struct flowi4 *fl4, __be32 dst, __be32 src,
					 u32 tos, int oif, u8 protocol,
					 __be16 sport, __be16 dport,
					 struct sock *sk)
{
	__u8 flow_flags = 0;

	if (inet_sk(sk)->transparent)
		flow_flags |= FLOWI_FLAG_ANYSRC;

	flowi4_init_output(fl4, oif, sk->sk_mark, tos, RT_SCOPE_UNIVERSE,
			   protocol, flow_flags, dst, src, dport, sport,
			   sock_i_uid(sk));
}

static inline struct rtable *ip_route_connect(struct flowi4 *fl4,
					      __be32 dst, __be32 src, u32 tos,
					      int oif, u8 protocol,
					      __be16 sport, __be16 dport,
					      struct sock *sk)
{
	struct net *net = sock_net(sk);
	struct rtable *rt;

	ip_route_connect_init(fl4, dst, src, tos, oif, protocol,
			      sport, dport, sk);

	if (!dst || !src) {
		rt = __ip_route_output_key(net, fl4);
		if (IS_ERR(rt))
			return rt;
		ip_rt_put(rt);
		flowi4_update_output(fl4, oif, tos, fl4->daddr, fl4->saddr);
	}
	security_sk_classify_flow(sk, flowi4_to_flowi(fl4));
	return ip_route_output_flow(net, fl4, sk);
}

static inline struct rtable *ip_route_newports(struct flowi4 *fl4, struct rtable *rt,
					       __be16 orig_sport, __be16 orig_dport,
					       __be16 sport, __be16 dport,
					       struct sock *sk)
{
	if (sport != orig_sport || dport != orig_dport) {
		fl4->fl4_dport = dport;
		fl4->fl4_sport = sport;
		ip_rt_put(rt);
		flowi4_update_output(fl4, sk->sk_bound_dev_if,
				     RT_CONN_FLAGS(sk), fl4->daddr,
				     fl4->saddr);
		security_sk_classify_flow(sk, flowi4_to_flowi(fl4));
		return ip_route_output_flow(sock_net(sk), fl4, sk);
	}
	return rt;
}

static inline int inet_iif(const struct sk_buff *skb)
{
	int iif = skb_rtable(skb)->rt_iif;

	if (iif)
		return iif;
	return skb->skb_iif;
}

extern int sysctl_ip_default_ttl;

static inline int ip4_dst_hoplimit(const struct dst_entry *dst)
{
	int hoplimit = dst_metric_raw(dst, RTAX_HOPLIMIT);

	if (hoplimit == 0)
		hoplimit = sysctl_ip_default_ttl;
	return hoplimit;
}

#endif	/* _ROUTE_H */